does it make sense to protect electrolytic coupling capacitor from ESD?

[SArepairman]

I built a little preamplifier, which features a AC coupled 50 ohm input.

I have a low voltage GDT sitting around, does it make sense to put ESD protection on a electrolytic coupling capacitor (polymer 16v)?

[moffy]

No. But 50ohm with an electrolytic coupling cap sounds a little strange. Electro's don't make good coupling caps in audio because they have a voltage dependent non linearity i.e. they introduce distortion. Why 50ohm?! sounds like something RF not audio.

[Richard Crowley]

Is this an audio circuit?  An RF circuit?  What is the nominal signal voltage here?
It really isn't possible to provide a useful response without knowing anything about the situation.
Is this an application where you expect large fault currents?  Like an antenna up in the air, or a long overhead transmission line?

What does "low-voltage" GDT mean? If it is > 16V then it provides no protection to the capacitor.
Furthermore, it doesn't make much sense to use a more expensive component to "protect" an inexpensive commodity component.
Like using a $20 circuit breaker to "protect" a 20-cent fuse.

Depending on the nominal signal voltage (not revealed here), it typically makes more sense to use diodes to protect the output.
There are many different protection circuits and schemes depending on details of the application not in evidence here.

[f5r5e5d]

ESD is seldom enough charge to put any appreciable V on larger uF to mF coupling caps

but the cap may be a fine short at ESD edge rates to your circuit's input devices that may want protection

[Conrad Hoffman]

I assume you've got the typical preamp output with some opamp or discrete circuit, a 50 ohm stabilization resistor and an AC coupling cap. The 50 ohms here has nothing to do with impedance matching or RF concerns, it just insures stable operation with cable capacitance. I see values of anywhere between 10 and 600 ohms, though 50 and 100 seem most common. In the history of audio I doubt a cap has ever been damaged by an ESD event short of a lightening strike. I'd never add protection. As for the coupling cap, though film is preferred, as long as the electrolytic is large enough, and remember it's likely in series with a similar cap in the power amp, you won't get distortion. The usual rule is 10X the value for the desired -3dB point, effectively a couple Hz.